As is known, many electrical or electronic appliances envisage a slow-consumption mode of operation, referred to as “stand-by mode”. In this mode, the electrical appliance is inactive as regards its normal operation (for example, display of images for a television set, sound reproduction for hi-fi equipment, etc.) but can be controlled in switching-on through a remote control. As is generally known, an electrical appliance in stand-by mode is in any case supplied through the electric-supply mains, such as domestic power. The energy consumption is due to the presence of a microcontroller, configured to receive and process possible commands issued by a remote controller and supplied for this purpose.
Considerable efforts have been made in the last years to limit current consumption in stand-by mode of electrical appliances, which, so far, generally have levels of consumption of a few watts. However, it is evident that, if the consumption in stand-by mode of a plurality of electrical appliances generally present in dwellings is considered, non-negligible daily consumption levels may be reached.
It is known from PCT Application No. WO2010/106113 (the disclosure of which is incorporated by reference), and shown in FIG. 1 herein, a power supply circuit for an electrical appliances. The power supply circuit 30 in FIG. 1, in particular a switch-mode power supply (SMPS) circuit of a flyback type, comprises a remotely activated start-up circuit 32 connected to a capacitor 18, which is in turn connected to a ground reference voltage GND. The start-up circuit 32 comprises a turn-on transistor 15 and a transducer 33, which can be remote-controlled and is configured to power-on, when activated, passage of a current there though. The transducer 33 is connected between a drain terminal D and a gate terminal G of the turn-on MOS transistor 15. The transducer 33 can be a photodiode configured so as to power-on passage of a current through it if activated by a light beam at a particular wavelength or within a range of wavelengths. The start-up circuit 32 also comprises a turn-off resistor 34 connected between the gate terminal G and the source terminal S of the turn-on transistor 15; finally a Zener diode 35 is connected between the gate terminal G and the source terminal S of the turn-on transistor 15, in parallel to the turn-off resistor 34.